1. Field of the Invention
This invention pertains generally to image capture devices, and more particularly to camera depth of field rendering.
2. Description of Related Art
Aperture stops of photographic lenses and cameras provide control of the amount of illumination reaching an image sensor (or photosensitive film). Aperture control, in combination with control of shutter speed, regulate the extent of light exposure when capturing an image. It will be recognized that use of fast shutter speeds or image capture in low light conditions require larger apertures to obtain a correct exposure. Conversely, smaller apertures are used for intense light conditions and slower shutter speeds to obtain correct exposure.
Lens aperture is typically expressed as an f-number, which is the ratio of focal length to effective aperture diameter. A lens often provides a set of marked “f-stops” that the f-number can be set to. Lower f-numbers are indicative of larger aperture openings. A change of “one f-stop” refers to a factor of √{square root over (2)} (e.g., about 1.41) change in f-number and corresponds to a factor of two change in the light intensity being passed through the lens when capturing an image.
Although small to medium sized cameras have become extremely popular with regard to their light weight, portability and low cost, they typically suffer from having severely limited aperture sizes. Toward providing sufficient lighting through these small aperture lenses, increasingly sensitive image sensors have been sought to allow these small cameras to be utilized with faster shutter speeds or in lower lighting conditions. However, obtaining sufficient lighting to capture an image does not make a small aperture lens equivalent to a conventional large aperture lens.
Accordingly, a need exists for an apparatus and/or a method which is capable of increasing the lens aperture of a camera-lens system while not increasing its size or cost. These needs and others are met within the present invention, which overcomes the deficiencies of previously developed camera systems and methods.